1. Field of the Invention
The present invention generally relates to a liquid delivery tube, and more particularly, to a catheter for dosing medication which encloses a flow restrictor tube within the catheter lumen.
2. Description of the Prior Art
It is well known that the flow rate of a fluid through a tube can be controlled by a flow restricting orifice, an internal second tube, tube, or micro-passage of various configurations in combination with the first tube. There are several common embodiments of this art in commercial use today. U.S. Pat. No. 3,951,147 to Tucher, et al, describes several flow restrictors including a long stainless steel tube which is wound around an infusion pump body, a long spiral groove formed by inserting a threaded wire into a tube, and other similar configurations.
U.S. Pat. No. 4,386,929 to Peery, et al, discusses a short capillary tube contained within a pump housing for regulating the flow rate of medication dispensed. He also mentions other types of flow restrictors such as porous plugs, fiber bundles, and porous films, all of which are contained within the pump housing.
This prior art suffers from the disadvantage that changing the flow rate requires the use of a different pump. This creates an inventory problem for users who wish to select from a variety of flow rates at the time of application of the infusion pump. In addition, these infusion pumps generally do not provide the capability of delivering fluid to more than one catheter at a time since each catheter would require its own flow restrictor to insure a proper flow rate through the catheter.
U.S. Pat. No. 4,741,733 to Winchell, et al, discloses a flow restrictor placed in the delivery tube system outside the pump body. This system is used where multiple catheters are required to adequately infuse medication into the body. The Winchell flow restrictor consists of a short restrictor tube contained within a plastic housing. Usually the flow restrictor is a glass micro-bore tube.
To vary flow rates, the flow restrictor housing must be removed from the infusion delivery system, and a flow restrictor having a different flow rate added to the infusion system. Branching connectors can also be added. In this way multiple catheters having different flow rates can be achieved. However, it is still necessary that an inventory of flow restrictors having different flow rates be maintained if the user wishes to vary the flow rates at the time of application of the infusion device.
In order to overcome the need to maintain an inventory of catheters or flow restrictors having different flow rates, it is desirable to have a catheter with a flow rate easily adjustable at the time of use. Such a catheter would enable only one catheter to be inventoried yet allow the user to adjust its flow rate to any flow rate desired at the time of use.
Accordingly, the current invention provides a new and improved catheter for dispensing fluids and medications from an infusion device. A new and improved catheter is provided which contains a flow restrictor within the catheter tube, the flow rate through the catheter being easily adjustable.
In accordance with these and many other objects of the current invention, a catheter tube with a flow restrictor tube located within has a flow rate which is adjustable by trimming the length of the flow restrictor and catheter tube assembly. The tubing could be trimmed at the time of manufacture or could be trimmed at a later time of use. Length markings to aid in trimming the tubing assembly, which are correlated with a flow rate through the catheter, can be placed on the outside of the catheter tubing by ink, or other suitable markings such as imbedding the markings in the tubing wall.
The flow restrictor tubing can be any flexible micro-bore tubing that can be easily trimmed without distorting the trimmed end. The flow restrictor tubing is positioned within the lumen of the catheter tubing so that no fluid will flow between the outside of the flow restrictor tubing and the wall of the lumen of the catheter tubing. The catheter can be attached to the infusion device after trimming by means of a Touhy-Borst connector, or by other suitable means.
As the catheter flow restrictor assembly is shortened by trimming, the flow rate will increase in linear proportion to the initial length of the flow restrictor tubing. For example, if the length of the flow restrictor tubing is cut in half, the flow rate will double.